Pedestal assembly of washing machine

ABSTRACT

A pedestal assembly of a washing machine, by which a user is facilitated to use a door of the washing machine supported by a pedestal to be positioned in a convenient place is disclosed. The pedestal assembly of a washing machine includes at least one leg coupled to a bottom surface of the washing machine, a pedestal provided under the washing machine to support the at least one leg, and at least one bracket rigidly fixed to at least one side of the pedestal, each bracket comprising a slot for fitting a corresponding leg therein.

This application claims the benefit of Korean Application No.P2004-007888, filed on Feb. 13, 2004, which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a washing machine, and moreparticularly, to a pedestal assembly provided under the washing machineto support at least one leg thereof.

2. Discussion of the Related Art

Generally, a washing machine is a representative home appliance forremoving filth or dirt attached to a laundry using a reaction betweenwater and detergent. A drum is vertically or horizontally arrangedwithin the washing machine in general. In case of the washing machinehaving the vertically arranged drum, a pulsator or agitator is providedwithin the drum so that a laundry can be washed by a water current andfriction generated by the pulsator or agitator. The washing machinehaving the vertically arranged drum is advantageous in washingperformance but has a disadvantage of entangling or wearing out thelaundry (or clothes).

In case of the washing machine having the horizontally arranged drum, aplurality of tumbling ribs are provided on an inner circumference of thedrum so that the laundry held in the drum is lifted upward by thetumbling ribs to fall. Hence, the laundry can be washed using the impactpower and friction generated from the falling. The washing machinehaving the horizontally arranged drum enables to avoid entangling orwearing out the clothes. Moreover, the washing machine having thehorizontally arranged drum is recently equipped with a drying functionto enable one-stop washing to drying, whereby user demand for thecorresponding washing machine rises.

However, in the washing machine having the horizontally arranged drum, adoor opening/closing the drum is provided to a front side of a washingmachine case. Hence, a user has to bend over to put/pull the laundryin/from the drum, which is very uncomfortable despite the advantages.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a pedestal assembly ofa washing machine that substantially obviates one or more of theproblems due to limitations and disadvantages of the related art.

An object of the present invention, which has been devised to solve theforegoing problem, lies in providing a pedestal assembly of a washingmachine, by which a user is facilitated to use a door of the washingmachine supported by a pedestal to be positioned in a convenient place.

Another object of the present invention, which has been devised to solvethe foregoing problem, lies in providing a pedestal assembly of awashing machine, by which the washing machine is conveniently fixed to apedestal.

Another object of the present invention, which has been devised to solvethe foregoing problem, lies in providing a pedestal assembly of awashing machine, by which vibration occurring on the washing machine puton a pedestal is effectively attenuated.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent to thosehaving ordinary skill in the art upon examination of the following ormay be learned from a practice of the invention. The objectives andother advantages of the invention will be realized and attained by thesubject matter particularly pointed out in the specification and claimshereof as well as in the appended drawings.

To achieve these objects and other advantages in accordance with thepresent invention, as embodied and broadly described herein, a pedestalassembly of a washing machine includes at least one leg coupled to abottom surface of the washing machine, a pedestal provided under thewashing machine to support the at least one leg, and at least onebracket rigidly fixed to at least one side of the pedestal, each bracketcomprising a slot for fitting a corresponding leg therein.

The pedestal may include at least one drawer. Each leg may include athread portion coupled to the bottom surface of the washing machine, anda head portion provided to a lower end of the thread portion to besupported by the pedestal.

The head portion includes a head extending from the lower end of thethread portion, and a housing accommodating the head. Herein, a gapexists between an end portion of the housing accommodating a topside ofthe head and an outer circumference of the thread portion.

Each bracket may include a protrusion extending downward in the vicinityof the slot to be fitted in the gap. The head portion may include a padprovided between the head and the housing. Herein, the slot has aU-shape.

Each bracket may include a protrusion extending downward in the vicinityof the slot to stably support a corresponding leg. Herein, each bracketis fixed to a lateral side of the pedestal by a locking member. And, thepedestal includes at least one concave recess, and wherein each bracketfurther comprises at least one protrusion to be fitted in the at leastone concave recess.

Each bracket includes a first portion including the slot, and a secondportion extending downward from the first portion to be fixed to thepedestal. Herein, the second portion vertically extends downward from anend portion of the first portion in the vicinity of a closed end portionof the slot.

In another aspect of the present invention, a pedestal assembly of awashing machine includes at least one leg coupled to a bottom surface ofa case of the washing machine, a pedestal provided under the case tosupport the at least one leg, and at least one bracket rigidly fixed toat least one side of the pedestal, each bracket comprising a firstportion having an open end to form a slot for fitting a correspondingleg therein, and a second portion extending downward from the firstportion to be fixed to the pedestal.

In a further aspect of the present invention, a washing machine includesa case, a drum rotatably provided within the case, a water supply systemsupplying water to the drum, a drain system draining the water, at leastone leg coupled to a bottom surface of the case, a pedestal providedunder the case to support the at least one leg, and at least one bracketrigidly fixed to at least one side of the pedestal, each bracketcomprising a first portion having an open end and the other closed endto form a slot for fitting a corresponding leg therein, and a secondportion extending downward from the first portion to be fixed to anouter wall of the pedestal by a screw.

The pedestal may include at least one drawer. Each leg includes a threadportion coupled to the bottom surface of the washing machine, a headextending from the lower end of the thread portion, and a housingaccommodating the head to be supported by a topside of the pedestal.

Herein, a gap exists between an end portion of the housing accommodatinga topside of the head and an outer circumference of the thread portion.The first portion may include a protrusion extending downward in thevicinity of the slot to be fitted in the gap. The head may include a padprovided between the head and the housing. The pedestal may include atleast one concave recess, and wherein the second portion furthercomprises at least one protrusion to be fitted in the at least oneconcave recess.

It is to be understood that both the foregoing explanation and thefollowing detailed description of the present invention are exemplaryand illustrative and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a perspective diagram of a washing machine provided with apedestal assembly according to the present invention;

FIG. 2 is a cross-sectional diagram of the washing machine in FIG. 1;

FIG. 3 is a perspective diagram of a pedestal, bracket, and leg of thepedestal assembly in FIG. 1; and

FIG. 4 is a cross-sectional diagram taken along line I-I of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Throughout the drawings, like elements are indicated using thesame or similar reference designations where possible.

FIGS. 1 and 2 show a washing machine provided with a pedestal assembly200 according to the present invention. A configuration of the washingmachine according to the present invention is explained in detail byreferring to the appended drawings as follows.

Referring to FIGS. 1 and 2, a case 100 of a washing machine includes abase plate 110, a wall 120, a front cover 130, and a top plate 140. Thewall 120 is provided on the base plate 110 to form rear and both lateralsides of the case 100. The front cover 130 is provided in front of thewall 120 to form a front side of the case 100. And, the top plate 140 isprovided over the wall 120 to form a topside of the case 100.

Referring to FIG. 2, a tub 310 is suspended within a case 100. For this,an upper part of the tub 310 is connected to a spring 301 fixed to thecase 100 and a lower part (or bottom surface) of the tub 310 isconnected to a damper 302 connected to a bottom surface of the case 100via a hinge. The above-provided spring 301 and damper 302 play a role inattenuating vibration occurring on the tub 310 in the course ofoperating a washing machine as well as elastically suspending the tub310 within the case 100.

A drum 320 is rotatably provided within the tub 310. For this, a motor330 is provided within the case 100, and more particularly, in rear ofthe tub 310. And, the drum 320 is connected to the motor 330 via a shaft331. A multitude of perforated holes 321 perforate a circumference ofthe drum 320, and a plurality of tumbling ribs 325 are provided on aninner circumference of the drum 320. Hence, water supplied to the tub310 enables to communicate between the drum 320 and the tub 310 via theperforated holes 321. A laundry held in the drum 320 is lifted upward tofall by the tumbling ribs 325 while the drum 320 is rotated. Hence,friction and impact energy sufficient for washing can be provided whenthe laundry falls by the tumbling ribs 325.

An opening 131 is provided to a front side of the case 100, i.e., thefront cover 130, so that a user can put/pull the laundry in/from thedrum 320, and a door is provided to open/close the opening 131. A gasket137 is provided between the opening 131 of the case 100 and the tub 310to prevent water/laundry held in the drum 320 and/or tub 310 fromleaking/escaping. And, a control panel 150, as shown in FIGS. 1 and 2,is provided to one side of the case 100, e.g., an upper side of the case100, to enable a user to operate the washing machine.

Meanwhile, a water supply system 340 and drain system 350 are providedwithin the case 100. The water supply system 340 includes an inlet valve341, an inlet hose 342, a detergent box 343, and an inlet bellows 344.The inlet valve 341 opens or closes a passage of water supplied fromoutside, and the inlet hose 342 connects the inlet valve 341 and thedetergent box 343. And, the inlet bellows 344 connects the detergent box343 and the tub 310. Once the inlet valve 341 is turned on, water ispassed through the inlet hose 342, detergent box 343, and inlet bellows344 in turn to be supplied to the tub 310. In this case, a detergentstored in the detergent box 343 is supplied to the water if necessary.

The drain system 350 includes a drain bellows 351, a drain pump 352, anda drain hose 353. The drain bellows 351 connects the tub 310 and thedrain pump 352. One end of the drain hose 353 is connected to the drainpump 352 and the other end of the drain hose 353 communicates withoutside of the case 100. Hence, once the drain pump 352 is driven, waterheld in the tub 310 is passed through the drain bellows 351, the drainpump 352, and the drain hose 353 in turn to be discharged outside.

Meanwhile, a pedestal assembly 200 according to the present invention,as shown in FIGS. 1 and 2, is provided under the case 100 of the washingmachine. The pedestal assembly 200 includes a plurality of legs 220connected to the case 100, a pedestal 210 provided under the case 100 tosupport the legs 220, and at least one bracket 230 preventing relativemotion between the pedestal 210 and each of the legs 200. Aconfiguration of the pedestal assembly is shown in detail in FIGS. 3 and4, which is explained in detail by referring to the drawings in thefollowing.

First of all, the leg 220 is coupled to a lower part (or bottom surface)of the case 100 of the washing machine. For this, a thread portion 221is provided to the leg 220. And, the leg 220, as shown in FIG. 2, isscrew-coupled to the lower part of the case 100, and more particularly,to a corner of the base plate 110. And, a head portion 225 is providedto a lower end of the thread portion 221. The head portion 225, as shownin FIG. 2, is supported by a topside of the pedestal 210. It ispreferable that the head portion 225 has a configuration enabling toabsorb shock or vibration transferred from the washing machine. Hence,the head portion 225 is explained in detail as follows.

Referring to FIG. 4, a head 226 extending from a lower end of the threadportion 221 and a housing 227 accommodating the head 226 are provided tothe head portion 225. The head 226 is formed of a hard material as wellas the thread portion 221. And, the head 226 is built in one body of thethread portion 221. The housing 227 is formed of a material enabling toabsorb vibration or shock such as a rubber based material. And, thehousing 227 accommodates a bottom side, lateral side, and topside of thehead 226. The housing, as shown in FIG. 4, accommodates an edge area ofthe topside of the head 226 rather than accommodating the entire topsidethereof. Hence, a gap 228 is formed, as shown in FIG. 4, between anouter circumference of the thread portion 221 and an end portion of thehousing 227 accommodating the topside of the head 226.

A pad 229 is further provided to the head portion 225 to enhancevibration-absorbing capability of the head portion 225. The pad 229, asshown in FIG. 4, is provided between a bottom side of the head 226 andthe housing 227 to absorb the top-to-bottom vibration transferred fromthe washing machine. Meanwhile, the pedestal 210 has a predeterminedheight. Preferably, the predetermined height corresponds to a heightfacilitating a user to open/close the door 135 of the washing machine.For this, the pedestal 210 can be manufactured into various productsdiffering in height, whereby a user conveniently selects to use thepedestal 210 having an appropriate height by considering an installationenvironment of the washing machine, user's height, and the like.

Furthermore, a drawer 215 is provided to the pedestal 210. And, thedrawer 215 can be drawn in a front direction of the washing machine. Auser can keep a detergent and the like in the drawer 215 to enhanceuser's convenience. The bracket 230 is fixed to the pedestal 210 andincludes a slot 233 for fitting the corresponding leg 220 therein. Thebracket 230 holds the leg 220 to prevent the washing machine on thepedestal 210 from being shaken by the vibration of the washing machineor sliding on the pedestal 210. In order to effectively attenuate thehorizontal vibration of the washing machine, the bracket 230 is formedof a spring carbon tool steel based material having an excellent elasticrestoring capability. A configuration of the bracket 230 is explained indetail as follows.

Referring to FIGS. 1, 3, and 4, the bracket 230 includes a first portion231 holding the leg 220 and a second portion 235 fixed to the pedestal210. The second portion 235 extends from the first portion 231 downward.For instance, the first and second portions 231 and 235, as shown inFIG. 1, can be provided to have an angle shape bent at a right angle toeach other. A slot 233 is provided to the first portion 231 to hold theleg 220, which is explained in detail in the following.

One of both ends of the slot 233, as shown in FIGS. 1 and 3, is open sothat the thread portion 221 of the leg 220 can be inserted in the slot233 is a horizontal direction. And, the other end of the slot 233 isclosed to hold the thread portion 221 of the leg 220 inserted in theslot 233 via the open one end. For instance, the slot 233 having theopen one end and the closed other end, as shown in FIGS. 1 and 3, canhave a U-shape. A width of the slot 233 is greater than a diameter ofthe thread portion 221 of the leg 220 and is smaller than a diameter ofthe head portion 225.

A protrusion 234, as shown in FIGS. 1 and 4, may extend from the firstportion 231 downward along a circumference of the slot 233. When thethread portion 221 of the leg 220 is fitted in the slot 233, theprotrusion 234 adheres closely to the leg 220 to effectively prevent theleg 220 from moving. Specifically, the protrusion 234, as shown in FIG.4, is fitted in a gap 228 provided to the head portion 225 of the leg220 to make the head portion 25 adhere closely to the pedestal 210.Hence, the bracket 230 enables to hold the leg 220 stably.

The second portion 235 of the bracket 230 vertically extends downwardfrom one end of the first portion 231 in the vicinity of the closed endof the slot. For instance, the second portion 235 is fixed to an outerwall of the pedestal 210 (e.g., a lateral side) by a locking member 240,such as a screw and the like. For this, at least one first hole 237 isprovided to the second portion 23 of the bracket 230 and a second hole211 confronting the first hole 237 is provided to the lateral side ofthe pedestal 210.

At least one concave recess 213 is provided to the pedestal 210 and atleast one protrusion 239 confronting the recess 213 is provided to thebracket 230. For instance, a pair of the recesses 213, shown in FIGS. 1and 4, is provided to the lateral side of the pedestal in parallel. Theprotrusion 239 is projected from the bracket 230 to be fitted in thecorresponding recess 213. And, the protrusion 239 can be formed by usinga pressing method.

Once the recess 213 and protrusion 239 are provided, the bracket 230 isprevented from being shaken by the vibration occurring on the washingmachine or the coupled portion coupled to the pedestal by the lockingmember 240 is prevented from being loosened by the vibration occurringon the washing machine. Besides, the recess 213 and protrusion 239determines a loading position of the bracket 230, whereby the bracket230 is facilitated to be quickly loaded on the correct position of thepedestal.

An assembling process of the pedestal assembly 200 is explained asfollows. The leg 20 is coupled to the corner of the lower part of thecase 100, and more particularly, to the corner of the base plate 110 viaa screw. The washing machine is then put on the pedestal 210. In doingso, the head portion 225 of the leg 220 is placed on a topside corner ofthe pedestal 210. Once the washing machine is put on the pedestal 210,the bracket 230 is fixed to the pedestal 210. Thus, the protrusion 239of the second portion 235 is fitted in the corresponding recess 213.And, the protrusion 234 of the first portion 234 is fitted in the gap228 of the head portion 225 of the leg 220 to be fixed thereto.Moreover, the locking member 240 is locked in both of the first hole 237of the bracket 230 and the second hole 211 of the pedestal 211.

As the bracket 230 is installed on the pedestal 210, the protrusion 234of the first portion 231 pushes the head 226 toward the pedestal 210 sothat the bottom side of the head portion 225 can adhere closely to thetopside of the pedestal 210. Thus, the washing machine can be stablyfixed to the pedestal 210.

A washing machine provided with the above-configured pedestal assembly200 according to the present invention is operated as described below.First, a laundry is put in the drum 320 and the door 135 is closed. Indoing so, a user can easily put the laundry in the drum via the door 135without bending his or her body since the pedestal 210 is provided belowthe case 100 of the washing machine. The control panel 150 is thenoperated. Once the washing machine is activated after setting washing,rinsing, dewatering, and drying cycles, the water supply system 340supplies a predetermined amount of water and detergent to the drum 320.As the drum 320 rotates, the laundry is lifted by the tumbling rib 325to fall. In doing so, the laundry is washed by the generated impactpower and the chemical reaction of detergent.

After completion of the washing cycle, the drain system 350 dischargesthe used water of the drum 320 and tub 310. After completion of drain,the water supply system 340 supplies water to the drum 320. The drum 320is then rotated to rinse the laundry. After completion of the rinsingcycle, the drain system 350 discharges the water of the drum 310. Inthis case, at least one washing cycle is carried out.

After completion of the rinsing cycle, the drum 320 is rotated at a highspeed so that water is separated from the laundry by a centrifugalforce. After the completion of the dewatering cycle, a user pulls thewashed and dewatered laundry out of the washing machine via the door135. If a drying function is further provided to the washing machine,hot air is supplied to the drum 320 to completely dry the laundry aftercompletion of the dewatering cycle. The user is then provided withcompletely dried laundry.

Meanwhile, the vibrations generated from the washing machine during theabove-explained operation are transferred to the leg 220 attached to thelower part of the case 100. The vertical vibration among the vibrationstransferred to the leg 220 is absorbed in the pad 239 and the housing227, whereas the horizontal vibration is effectively attenuated by thebracket 239 having elasticity. The washing machine 210 is prevented fromslipping on the pedestal 210 as the bracket 230 stably holds thecorresponding leg 220.

Accordingly, the present invention has the following advantages oreffects.

First of all, the pedestal assembly raises the levels of the washingmachine including the door, thereby facilitating a user to put/pull alaundry in/from the drum without bending his body. Secondly, in order tofix the washing machine to the pedestal, the leg of the washing machineis fitted in the slot of the bracket and the bracket is then fixed tothe pedestal using the locking member. Hence, installation can be doneconveniently and easily. Moreover, in re-installing the washing machineafter moving, the entire elements of the pedestal assembly can bereused.

Thirdly, the pad and housing enabling to absorb the vibration areprovided to the leg, thereby enabling effective absorption of thevibrations occurring in the washing machine. Fourthly, the bracket makesthe head portion of the leg adhere closely to the pedestal and aplurality of the brackets prevent the washing machine from slipping in ahorizontal direction. Therefore, the washing machine is stably fixed tothe pedestal without slipping thereon. Finally, the concave recess andprotrusion, which are correspondingly provided to the pedestal and thebracket, respectively, prevent the bracket from being shaken or thecoupling portion from being loosened. Furthermore, the concave recessand protrusion determine the loading position of the bracket, therebyenabling a quick load of the bracket thereon.

The present invention is applicable to a washing machine having a doorprovided to its topside as well as a washing machine having a doorprovided to its front side. Furthermore, the present invention isapplicable to such a home appliance as a dryer and the like as well as awashing machine.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover such modifications andvariations, provided they come within the scope of the appended claimsand their equivalents.

1. A pedestal assembly of a washing machine, comprising: at least oneleg coupled to a bottom surface of the washing machine; a pedestalprovided under the washing machine to support the at least one leg; andat least one bracket rigidly fixed to at least one side of the pedestal,each bracket comprising a slot for fitting a corresponding leg therein.2. The pedestal assembly of claim 1, wherein the pedestal comprises atleast one drawer.
 3. The pedestal assembly of claim 1, each legcomprising: a thread portion coupled to the bottom surface of thewashing machine; and a head portion provided to a lower end of thethread portion to be supported by the pedestal.
 4. The pedestal assemblyof claim 3, the head portion comprising: a head extending from the lowerend of the thread portion; and a housing accommodating the head.
 5. Thepedestal assembly of claim 4, wherein a gap exists between an endportion of the housing accommodating a topside of the head and an outercircumference of the thread portion.
 6. The pedestal assembly of claim5, each bracket further comprising a protrusion extending downward inthe vicinity of the slot to be fitted in the gap.
 7. The pedestalassembly of claim 4, the head portion further comprising a pad providedbetween the head and the housing.
 8. The pedestal assembly of claim 1,wherein the slot has a U-shape.
 9. The pedestal assembly of claim 1,each bracket further comprising a protrusion extending downward in thevicinity of the slot to stably support a corresponding leg.
 10. Thepedestal assembly of claim 1, wherein each bracket is fixed to a lateralside of the pedestal by a locking member.
 11. The pedestal assembly ofclaim 1, wherein the pedestal comprises at least one concave recess, andwherein each bracket further comprises at least one protrusion to befitted in the at least one concave recess.
 12. The pedestal assembly ofclaim 1, each bracket comprising: a first portion including the slot;and a second portion extending downward from the first portion to befixed to the pedestal.
 13. The pedestal assembly of claim 12, whereinthe second portion vertically extends downward from an end portion ofthe first portion in the vicinity of a closed end portion of the slot.14. A pedestal assembly of a washing machine, comprising: at least oneleg coupled to a bottom surface of a case of the washing machine; apedestal provided under the case to support the at least one leg; and atleast one bracket rigidly fixed to at least one side of the pedestal,each bracket comprising a first portion having an open end to form aslot for fitting a corresponding leg therein, and a second portionextending downward from the first portion to be fixed to the pedestal.15. The pedestal assembly of claim 14, each leg comprising: a threadportion coupled to the bottom surface of the washing machine; and a headportion provided to a lower end of the thread portion to be supported bythe pedestal.
 16. The pedestal assembly of claim 15, the head portioncomprising: a head extending from the lower end of the thread portion;and a housing accommodating the head.
 17. The pedestal assembly of claim16, wherein a gap exists between an end portion of the housingaccommodating a topside of the head and an outer circumference of thethread portion.
 18. The pedestal assembly of claim 17, the first portionfurther comprising a protrusion extending downward in the vicinity ofthe slot to be fitted in the gap.
 19. The pedestal assembly of claim 16,the head portion further comprising a pad provided between the head andthe housing.
 20. The pedestal assembly of claim 14, wherein the pedestalcomprises at least one concave recess, and wherein the second portionfurther comprises at least one protrusion to be fitted in the at leastone concave recess.
 21. A washing machine, comprising: a case; a drumrotatably provided within the case; a water supply system supplyingwater to the drum; a drain system draining the water; at least one legcoupled to a bottom surface of the case; a pedestal provided under thecase to support the at least one leg; and at least one bracket rigidlyfixed to at least one side of the pedestal, each bracket comprising afirst portion having an open end and the other closed end to form a slotfor fitting a corresponding leg therein, and a second portion extendingdownward from the first portion to be fixed to an outer wall of thepedestal by a screw.
 22. The washing machine of claim 21, wherein thepedestal comprises at least one drawer.
 23. The washing machine of claim21, each leg comprising: a thread portion coupled to the bottom surfaceof the washing machine; a head extending from the lower end of thethread portion; and a housing accommodating the head to be supported bya topside of the pedestal.
 24. The washing machine of claim 23, whereina gap exists between an end portion of the housing accommodating atopside of the head and an outer circumference of the thread portion.25. The washing machine of claim 24, the first portion furthercomprising a protrusion extending downward in the vicinity of the slotto be fitted in the gap.
 26. The washing machine of claim 23, the headfurther comprising a pad provided between the head and the housing. 27.The washing machine of claim 21, wherein the pedestal comprises at leastone concave recess, and wherein the second portion further comprises atleast one protrusion to be fitted in the at least one concave recess.